The present invention relates to quench-hardening of pipes of large diameter and when in horizontal disposition; and more particularly the invention relates to improvements in quench-hardening equipment wherein an induction heater for heating the pipe is rather closely association with groups of nozzles for quenching the pipe from the inside and from the outside.
Known equipment for quench-hardening operate for example by moving a pipe in vertical disposition of its axis through an induction heater and through a nozzle arrangement. Alternatively, the heated tube is dipped into a quenching bath. Pipes of 20 inch diameter and larger and at a length equal to or even in excess of 50 ft. are quite difficult to treat in that fashion, particularly because the vertical disposition requires rather complicated and large equipment.
Quench-hardening of pipes in horizontal disposition has not yet been successfully practiced for such large pipes. The equipment used here in attempts along that line uses rolls supporting the pipe at its inside apex and ahead of that part of the quenching equipment that sprays on the inside. Alternatively the inside quenching head is supported centrally in that portion of the pipe which has already been treated and quench hardened.
The problem of this approach which has not yet been solved is to be seen in the following. The cross-section of the pipe which has been heated to the hardening temperature is deformed by the force of gravity acting on the pipe, so that the contour encountered by the quenching nozzles is no longer a circular one. As the nozzle-to-pipe wall spacing is thus subject to local variation the intensity of quenching differs accordingly along the pipes periphery. Additionally, the centering of the quenching head operating on the inside becomes unreliable. Actually, the extent of deviation of the pipe from a circular cross-sectional contour is so great, and depends on so many different factors that a sufficiently uniform quench-hardening has not yet been practiced in that manner.